Optimum nitrogen fertilization of Calophyllum inophyllum seedlings under greenhouse conditions

Abstract

A greenhouse pot experiment was conducted to study the effects of nitrogen fertilization on Calophyllum inophyllum seedlings grown with 0, 50, 100, 150, 200, 300, 400 and 600 mg N per seedling according to exponential functions. Seedling height, root collar diameter, leaf area and total biomass increased with increasing fertilization from 0 to 200 mg N per seedling and decreased with further increase in fertilization from 300 to 600 mg N per seedling. The net photosynthetic rate, stomatal conductance, intercellular CO 2 concentration and transpiration rate of C. inophyllum seedlings showed a unimodal parabolic trend, with peak values of 7.29 mmol$m -2 $s -1 , 0.071 mol$m -2 $s -1 , 220 mmol$mol -1 and 1.34 mmol$m -2 $s -1 , respectively, when the rate of fertilization was 200 mg N per seedling. Photosynthetic gas exchange parameters were significantly different among nitrogen treatments. Based on the critical values of leaf N and P concentration and N/P ratio, the optimum amount of nitrogen of C. inophyllum seedlings was 200-400 mg per seedling for leaf N and P concentration, and 100-400 mg per seedling for N/P ratio. It was concluded that 200-400 mg N per seedling was the most suitable nitrogen range for C. inophyllum seedlings.

Gas Exchange and Nitrogen Compartmentalization of Eggplant under Nitrogen and Silicon Doses

“…The increase of the photosynthetic rate is probably due to the N action in the composition of the chlorophyll molecules, in which the active sites responsible for photosynthesis are found [25,26], as observed by Zhang et al [27]. At lower doses of N, probably occurred a decrease in the turgescence potential of foliar tissues, causing stomata closure, increased CO 2 diffusion resistance, and a consequent decrease in the photosynthetic rate [24,26].…”